1 -√a-√b
2 x-1+x-4=2x-5
1-x<=0,x-4<=0
解得 1<=x<=4
3 1/x-1/y=(y-x)/xy=-√12/√8=-√6/2
4 面积比是4:9 差是30,所以面积分别是30/5 *4=24
30/5*9=54,分别是,24M^2,54m^2
1. (b-a)/(√a-√b)=(√b+√a)(√b-√a)/(√a-√b)=-√b-√a
2. |1-x|-√(x2-8x+16)=2x-5
所以1-x≤0,x-4≤0
得1≤x≤4
3.1/x-1/y=(y-x)/xy=-√12/√8=(-√6)/2
4.24m^2和54m^2